hope four lights. charge issue

I have one of the hope 4 lights. On recharging I plug it in, LED goes red, then back to green then red...
thinking it's a connector issue but....
I suppose I could measure voltage across the circuit with the light attached...
any thoughts?

Connectors. Mine has been doing this for a while, rectified by charging using the extension lead that comes with it for putting the battery in your backpack, between the charger and the battery. Havent had chance send it back as need the lights all the time at the moment.